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.Dd December 14, 2021
.Dt MAC_PRIORITY 4
.Os
.Sh NAME
.Nm mac_priority
.Nd "policy for scheduling privileges of non-root users"
.Sh SYNOPSIS
To compile the mac_priority policy into your kernel, place the following lines
in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "options MAC"
.Cd "options MAC_PRIORITY"
.Ed
.Pp
Alternately, to load the mac_priority policy module at boot time,
place the following line in your kernel configuration file:
.Bd -ragged -offset indent
.Cd "options MAC"
.Ed
.Pp
and in
.Xr loader.conf 5 :
.Bd -literal -offset indent
mac_priority_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
policy grants scheduling privileges based on
.Xr group 5
membership.
Users or processes in the group
.Sq realtime
(gid 47) are allowed to run threads and processes with realtime scheduling
priority.
Users or processes in the group
.Sq idletime
(gid 48) are allowed to run threads and processes with idle scheduling
priority.
.Pp
With the
.Nm
realtime policy active, privileged users may use the
.Xr rtprio 1
utility to start processes with realtime priority.
Privileged applications can promote threads and processes to realtime
priority through the
.Xr rtprio 2
system calls.
.Pp
When the idletime policy is active, privileged users may use the
.Xr idprio 1
utility to start processes with idle priority.
Privileged applications can demote threads and processes to idle
priority through the
.Xr rtprio 2
system calls.
.Ss Privileges Granted
The realtime policy grants the following kernel privileges to any process
running with the realtime group id:
.Bl -inset -offset indent -compact
.It Dv PRIV_SCHED_RTPRIO
.It Dv PRIV_SCHED_SETPOLICY
.El
.Pp
The kernel privilege granted by the idletime policy is:
.Bl -inset -offset indent -compact
.It Dv PRIV_SCHED_IDPRIO
.El
.Ss Runtime Configuration
The following
.Xr sysctl 8
MIBs are available for fine-tuning this MAC policy.
All
.Xr sysctl 8
variables can also be set as
.Xr loader 8
tunables in
.Xr loader.conf 5 .
.Bl -tag -width indent
.It Va security.mac.priority.realtime
Enable the realtime policy.
(Default: 1).
.It Va security.mac.priority.realtime_gid
The numeric gid of the realtime group.
(Default: 47).
.It Va security.mac.priority.idletime
Enable the idletime policy.
(Default: 1).
.It Va security.mac.priority.idletime_gid
The numeric gid of the idletime group.
(Default: 48).
.El
.Sh SEE ALSO
.Xr idprio 1 ,
.Xr rtprio 1 ,
.Xr rtprio 2 ,
.Xr mac 4
.Sh HISTORY
MAC first appeared in
.Fx 5.0
and
.Nm
first appeared in
.Fx 13.1 .
